Because they do not corrode, are light weight, and are easy to clean, unlike metal conveyor belts, plastic conveyor belts are used widely, especially in conveying food products. Modular plastic conveyor belts are made up of molded plastic modular links, or belt-modules, that can be arranged side by side in rows of selectable width. A series of spaced apart link ends extending from each side of the modules include aligned apertures to accommodate a pivot rod. The link ends along one end of a row of modules are interconnected with the link ends of an adjacent row. A pivot rod journaled in the aligned apertures of the side-by-side and end-to-end connected modules forms a hinge between adjacent rows. Rows of belt modules are connected together to form an endless conveyor belt capable of articulating about a drive sprocket.
The belts may be straight running or in many industrial applications, conveyor belts are used to carry products along paths including curved segments. Belts capable of flexing sidewise to follow curved paths are referred to as side-flexing, turn, or radius belts. As a radius belt negotiates a turn, the belt must be able to fan out because the edge of the belt at the outside of the turn follows a longer path than the edge at the inside of the turn. In order to fan out, a modular plastic radius belt typically has provisions that allow it to collapse at the inside of a turn or to spread out at the outside of the turn.
Apertures slotted in the direction of travel of the belt are commonly provided in the link ends on at least one side of the modules to facilitate the collapsing and spreading of the belt.
In order to provide for conveying of objects up and down inclines without slippage, it has been known to provide the top surface of the belt modules with a high friction surface. There have been many attempts at attaching the high friction conveying surface, which is typically an elastomeric or other high friction material, to the top of the belt module, which is typically formed from a rigid plastic suitable for use in a modular belt.
As proposed in U.S. Pat. No. 5,361,893 and U.S. Pat. No. 5,507,383, the rubber is molded to the flat top surface of the module relying on the thermal bonding between the rubber and the plastic surface. In practice, this bonding does not provide sufficient strength, particularly if the bonding area is relatively small, as is the case for flush grid and radius belts. Further, the thermal bonding requires a suitable chemical formulation for the rubber compound and restricts the number of usable material combinations.
Accordingly, what is needed is an improved structure and method for attaching a high friction conveying surface to the top of a belt.